US3723597A - Calcining phosphate minerals - Google Patents

Calcining phosphate minerals Download PDF

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Publication number
US3723597A
US3723597A US00110811A US3723597DA US3723597A US 3723597 A US3723597 A US 3723597A US 00110811 A US00110811 A US 00110811A US 3723597D A US3723597D A US 3723597DA US 3723597 A US3723597 A US 3723597A
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United States
Prior art keywords
mineral material
temperature
kiln
calcining
exothermic reaction
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Expired - Lifetime
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US00110811A
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English (en)
Inventor
F Dambrine
G Gross
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Fives Lille Cail
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Fives Lille Cail
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/01—Treating phosphate ores or other raw phosphate materials to obtain phosphorus or phosphorus compounds
    • C—CHEMISTRY; METALLURGY
    • C05—FERTILISERS; MANUFACTURE THEREOF
    • C05B—PHOSPHATIC FERTILISERS
    • C05B13/00—Fertilisers produced by pyrogenic processes from phosphatic materials
    • C05B13/02—Fertilisers produced by pyrogenic processes from phosphatic materials from rock phosphates

Definitions

  • the present invention relates to improvements in the calcination of a phosphate or analogous mineral material, which is used to enrich the mineral material by decomposing the carbonates contained therein into their constituent elements which are subsequently removed.
  • this conventional calcining treatment gives rise to an exothermic reaction which begins at a temperature of the order of about 400 C. to 600 C.
  • This exothermic reaction is probably due to the combustion of organic matter contained in the mineral material which comes to the surface of the mineral material.
  • the heat produced by this exothermic reaction is utilized, together with a portion of the calories furnished by the burner which produces the hot gases, to dry the mineral material and to raise its temperature to the above-indicated combustion temperature.
  • normal exothermic reaction temperature means the average temperature at which the major portion of the mineral material reacts when the temperature of the material is slowly raised, it being understood that the reaction begins at a temperature lower than this normal temperature and proceeds at temperatures in excess of such normal, i.e., average, temperature of reaction.
  • the calories liberated by the exothermic reaction at a temperature higher than the normal reaction temperature are utilized to calcine the mineral material and possibly to raise the temperature of the remaining fraction of the mineral material above the normal exothermic reaction temperature, which makes it possible to reduce the consumption of the burner.
  • the temperature of the mineral material before its introduction into the high temperature zone, the temperature in this zone and the quantity of the fraction of the mineral material to be introduced thereinto depend on the treatment conditions and the type of mineral material to be treated. The optimum choice of these parameters will be readily established by those skilled in the art without undue experimentation so as to recover at least a major part and possibly all of the exothermic reaction heat energy.
  • the fraction of the mineral material introduced into the high temperature zone is preferably classified so that only particles of minimum size are used, such small particles presenting a minimum thermal inertia and thus permitting rapid heating thereof.
  • the installation of the present invention comprises a drying chamber for the mineral material, a tubular rotary kiln, and a cooling chamber.
  • the mineral material and the heating gases may be circulated countercurrently through the kiln, a fraction of the material being removed before the mineral material is introduced into the kiln at one end thereof and this fraction being circulated and introduced into the kiln at the other end thereof where the burner is positioned so that the fraction of the mineral material passes through a high temperature zone adjacent the burner.
  • This invention is applicable to the calcination of mineral material containing phosphates as well as other mineral materials whose thermal treatment produces an exothermic reaction liberating a quantity of heat at a temperature lower than the maximum temperature of the treatment.
  • FIGS. 1 to 3 schematically illustrate three different installations according to the invention and useful, in the process thereof.
  • the drier may be of any known type used for drying particulate mineral material, whether pulverulent or granular.
  • the installation also comprises a long tubular rotary kiln 12, a
  • cooling chamber 14 of'any known type and a conventional classifier 15 for particulate material.
  • Each apparatus in this installation (and in the embodiments shown in FlGS.2'and 3) may be of conventional structure, and the present invention is not concerned with their structural features.
  • a burner 16 is positioned at the output end B of the kiln whence the calcined mineral material is discharged.
  • the hot gases produced by the combustion of a combustible fuel in the burner circulate through the kiln in a direction counter-current to the direction of flow of the major portions of the mineral material introduced into the kiln at input end A, the direction of flow of the hot gases being shown by the arrows in full lines while the direction of flow of the mineral material is indicated by the arrows in broken lines.
  • the mineral material is first introduced into the drying chamber where the hot gases exhausted from the kiln are used to dry and pre-heat the material.
  • the material is heated in the drying chamber 10 to a temperature of about 400 C. to 600 C. and the gases which enter the chamber at a temperature of about 1,000 C. to l,200 C. are exhausted from the drying chamber into the atmosphere at a temperature of about 120 C.
  • the drying chamber 10 As the dried and pre-heated mineral material leaves the drying chamber 10, a portion thereof is introduced into the kiln at. input end A which is opposite output end B where the burner 16 is positioned. Another portion of the material is, however, separated from the dried and pre-heated material and directed to the classifier where this other portion is separated into a coarse fraction and a fine fraction. The coarse fraction is returned to the first portion of the mineral material and enters the kiln at input end A. The fine fraction of the mineral material is introduced in the kiln at output end B ofthe kiln where the burneris positioned.
  • the mineral material proceeds through the kiln, its temperature is raised to about 950 C. to l,000 C., at which temperature it is calcined.
  • the calories necessary to raise the temperature of the mineral material from the combustion temperature of the organic matter contained therein to the calcining temperature thereof and to effectuate the decarbonization are produced by burner 16 and by the exothermic reaction produced in the fraction of the mineral material introduced in the high temperature zone of the kiln adjacent to end B.
  • the secondary air necessary for the combustion is at least partially provided by the hot air coming from cooling chamber 14 at a temperature of about 500 C. to 600 C.
  • the total charge of the mineral material introduced into the kiln is discharged at output end B of the kiln and conveyed into the cooling chamber 14 where cold air is introduced to contact the calcined material and lower its temperature from about 850950 C. to about l20 C., the heat exchange between the cold air and the hot mineral material raising the temperature of the air so that it provides a source of hot combustion air for the kiln, as hereinabove described and shown in FIG. 1.
  • the long tubular rotary kiln of FIG. 1 is replaced by a preheater arrangement consisting of a battery of cyclones 20 and a short rotary kiln 22 equipped with burner 24 at the output end B thereof, opposite to input end A which receives the pre-heated mineral material from the pre-heater arrangement.
  • the calcined material is cooled in cooling chamber 14
  • the operation of this installation is analogous to that described hereinabove in connection with the installation of FIG. 1 and being self-evident from the drawing wherein the flow of the mineral material is again shown by the arrows in broken lines while the flow of the hot gases is shown in full lines.
  • the mineral material coming from drying chamber 10' is conveyed to classifier 15' whence the fine fraction of the material is directed into end B of the kiln while a coarse fraction is introduced at a temperature of about C. into the pre-heater arrangement 20 where the temperature of the material is progressively raised to a range of 600 C. to 800 C. by the hot gases 1 exhausted from kiln 22 and counter-currently circuheat the mineral material is provided by the exothermic reaction produced in the later stages of the pre-heater arrangement and possibly at the input end of kiln 22.
  • the gases exhausted from kiln 22 at a temperature of about 900l,000 C. passthrough the pre-heater arrangement and are finally .introduced into the drying chamber at a temperature of about 600800 C. whence they are exhausted into the atmosphere at a temperature of about 120 C.
  • the short kiln in this installation is used almost exclusively for calcining the mineral material.
  • the calories required to bring the mineral material coming from the preheater arrangement to the calcining temperature are provided partly by burner 24 and partly by the exothermic reaction which the fraction of the mineral material introduced at B undergoes in the kiln.
  • the mineral material leaves the pre-heater arrangement 20 at a temperature of about 400500 C. and, since it is introduced into the high temperature zone of the kiln adjacent the burner 24, its temperature is rapidly raised.
  • the exothermic reaction consequently is produced primarily at a temperature higher than the normal exothermic reaction temperature of the material.
  • the calories provided by this combustion therefore, have a thermal level superior to that in conventional calcining installations of this type where the material and the hot gases flow counter-currently through the calcining kiln. Consequently, these calories may be utilized to effectuate at least partly the decarbonization of the mineral material. Therefore, this embodiment, too, permits the calorific consumption of the installation to be reduced.
  • At least a fraction of the mineral material is introduced into a high temperature zone of the kiln at a temperature below the normal exothermic reaction temperature of the material and the temperature of the material is rapidly or abruptly raised in this zone above this normal exothermic reaction temperature, the terms rapidly and abruptly" being interchangeable for purposes of this invention.
  • a process for calcining a mineral material which undergoes an exothermic reaction at a temperature below the calcining temperature of the mineral material comprising the step of rapidly raising the temperature of at least a fraction of the mineral material from a temperature lower than the normal exothermic reaction temperature of the mineral material to one in excess thereof whereby the exothermic reaction in said fraction of the mineral material proceeds at said higher temperature, and calcining the mineral material.
  • An installation for calcining a mineral material which undergoes an exothermic reaction at a temperature below the calcining temperature of the mineral material comprising pre-heating apparatus for preheating the mineral material, a rotary calcining kiln having an input end and an output end, a burner positioned at one of the kiln ends and producing hot gases flowing through the kiln, said one end of the kiln being connectedto the pre-heating apparatus .and receiving at least a fraction of the mineral material therefrom,
  • An installation for calcining amineral material which undergoes an exothermic reaction at a temperature below the calcining temperature of the mineral material comprising pre-heating apparatus for preheating the mineral material, means for removing a fraction of the pre-heated material from the pre-heating apparatus, a rotary calcining kiln having an input end and an output end, the means for removing the fraction of the pre-heated material being arranged intermediate the pre-heating apparatus and the kiln, a classifier for separating the removed fraction of the mineral material into a coarse and a fine portion, means for directing the coarse portion to the input end of the kiln, a burner positioned at the output end of the kiln and producing hot gases flowing through the kiln,

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Geology (AREA)
  • Environmental & Geological Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Muffle Furnaces And Rotary Kilns (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
  • Furnace Details (AREA)
  • Fertilizers (AREA)
  • Processing Of Solid Wastes (AREA)
US00110811A 1970-01-23 1971-01-29 Calcining phosphate minerals Expired - Lifetime US3723597A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7002404A FR2076680A5 (enrdf_load_stackoverflow) 1970-01-23 1970-01-23

Publications (1)

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US3723597A true US3723597A (en) 1973-03-27

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US00110811A Expired - Lifetime US3723597A (en) 1970-01-23 1971-01-29 Calcining phosphate minerals

Country Status (8)

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US (1) US3723597A (enrdf_load_stackoverflow)
JP (1) JPS5424999B1 (enrdf_load_stackoverflow)
BE (1) BE761721A (enrdf_load_stackoverflow)
DE (1) DE2103065C3 (enrdf_load_stackoverflow)
ES (1) ES387480A1 (enrdf_load_stackoverflow)
FR (1) FR2076680A5 (enrdf_load_stackoverflow)
GB (1) GB1320464A (enrdf_load_stackoverflow)
OA (1) OA03559A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3891383A (en) * 1972-12-06 1975-06-24 Ishikawajima Harima Heavy Ind Rotary kiln apparatus with suspension preheater having burner for calcining
US3914098A (en) * 1973-11-09 1975-10-21 Ishikawajima Harima Heavy Ind Suspension-type preheating system for powdery raw materials
US4325928A (en) * 1979-03-01 1982-04-20 Albright & Wilson Limited Rock treatment process
RU2349559C2 (ru) * 2003-10-29 2009-03-20 Ф.Л. Смидт А/С Способ и установка для подогрева порошкообразного или пылевидного материала

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2423440A1 (fr) * 1978-04-20 1979-11-16 Fives Cail Babcock Procede et installation pour la calcination a haute temperature des minerais de phosphate
IL68400A (en) * 1983-04-14 1986-03-31 Imi Tami Institute Research Method for the beneficiation of phosphate rock
US4557909A (en) * 1984-09-10 1985-12-10 Tennessee Valley Authority Method to improve acidulation quality of North Carolina phosphate rock

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2965366A (en) * 1957-08-09 1960-12-20 Richard F O'mara Kiln process having increased thermal efficiency
US3385580A (en) * 1963-11-04 1968-05-28 Escher Wyss Ag Heat transfer from waste gas of a cement kiln to pulverulent raw material

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2965366A (en) * 1957-08-09 1960-12-20 Richard F O'mara Kiln process having increased thermal efficiency
US3385580A (en) * 1963-11-04 1968-05-28 Escher Wyss Ag Heat transfer from waste gas of a cement kiln to pulverulent raw material

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3891383A (en) * 1972-12-06 1975-06-24 Ishikawajima Harima Heavy Ind Rotary kiln apparatus with suspension preheater having burner for calcining
US3914098A (en) * 1973-11-09 1975-10-21 Ishikawajima Harima Heavy Ind Suspension-type preheating system for powdery raw materials
US4325928A (en) * 1979-03-01 1982-04-20 Albright & Wilson Limited Rock treatment process
RU2349559C2 (ru) * 2003-10-29 2009-03-20 Ф.Л. Смидт А/С Способ и установка для подогрева порошкообразного или пылевидного материала

Also Published As

Publication number Publication date
DE2103065A1 (de) 1971-10-14
DE2103065B2 (de) 1974-09-05
GB1320464A (en) 1973-06-13
FR2076680A5 (enrdf_load_stackoverflow) 1971-10-15
JPS5424999B1 (enrdf_load_stackoverflow) 1979-08-24
OA03559A (fr) 1971-03-30
DE2103065C3 (de) 1975-06-05
ES387480A1 (es) 1973-12-16
BE761721A (fr) 1971-07-01

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